1. Field of the Invention
The present invention relates to an optical information recording medium in the form of a magneto-optical recording disk (90 mm ROM disk, 130 mm ROM disk, and the like) for a mark edge recording method used in a magneto-optical disk drive device, a CD-ROM device, a CD-R device, or the like.
2. Discussion of Background
Conventionally, the sector format for this type of magneto-optical recording disk is stipulated. Various types of format configurations have been proposed. Basically, the format comprises an address section, a flag section, a data section, and a buffer section.
Under the present ISO (International Standards Organization) standards, the sector format for a 90 mm magneto-optical recording disk is standardized as shown in FIG. 7, and for a 130 mm magneto-optical recording disk as shown in FIG. 8 (for 1024 user bytes) and as shown in FIG. 9 (for 512 user bytes). These correspond to sector formats for a continuous servo tracking method (composite continuous tracking method) for detecting a tracking error signal using, for example, a push-pull method.
The main areas in the figures will now be explained. An area SM (sector mark) indicates an area for detecting the head of a sector. Areas VFO1 to VFO3 show a continuously repeated data pattern for reliably reproducing data, even when there is a change in disk rotation, and are used for generating a clock for reading the data with a PLL (phase-locked loop) being locked in this pattern. An AM (address mark) shows an initial detection position (synchronous position) for reading an address code data, into which a special code pattern is inserted. An area SYNC or an area Sync is used for synchronous signals for a data section. An area ID shows an address, and an area CRC is used for a code for detecting errors in the ID section. An area ODF (offset detection flag=mirror surface section) is a mark region for detection of an offset for detecting tracking errors using the push-pull method, and is formed in a mirror surface area without either grooves or preformatted data. An area GAP shows a region without data with a specified byte. An area FLAG shows a flag region indicating that a write-in has been performed. An area ALPC (Auto Laser Power Control) shows a blank region which is a test section for controlling the power level of a laser beam source.
These sector formats are standardized so that they are suitable for a CAV (Constant Angular Velocity) code, a (2, 7) RLL modulating code (RLL is an abbreviation for Run Length Limited), and a mark position recording method.
In addition, for the current ISO standards, activities are progressing for the formulation of the next generation of standards, aiming at high speed and high density. Various methods have been proposed for the high speed and high density required for the next generation. One of these proposals is to combine MCAV (Modified CAV), the (1, 7) RLL modulation code, and the mark edge recording method. Specifically, if the mark edge recording method, which is suitable for high density recording in the next generation of standards, is adopted, the (1, 7) RLL modulation code will be the most suitable data modulation code.
In the case where a method is adopted which combines this type of MCAV, (1, 7) RLL modulation code, and mark edge recording method, it is obvious that the sector format for the current ISO standards cannot be used without modification, and some changes and innovations are necessary to eliminate problems of the following types:
First, the number of bits for one byte is changed by changing the modulation code used (modulation code without DC-free .characteristics). Specifically, with a (2, 7) RLL modulation code, there are 16 bits per byte, while with a (1, 7) RLL modulation code, there are 12 bits per byte. In addition, the AM, the VFO1 to VFO3, and the Sync pattern and others, must also be changed to suit the modulation code used.
Second, changing the recording method from a mark position recording method to the mark edge recording method, changes the shape of a prepit preformatted in the ID section of the disk, and lengthens the prepit, so that it is necessary to provide a device which minimizes the adverse effects on a tracking control system. Also, a characteristic problem in the mark edge recording method is that because the modulated data is preformatted by an NRZI code (Non Return to Zero Inverted code) pattern, it may occur that the prepit is not completed, depending upon the number of 1's in the modulated data, and if this takes place, the prepit becomes discontinued part way through. In such a case, a means is required to ensure that the prepit is not incomplete and is not discontinued part way through.
FIG. 10 shows this situation. FIG. 10 schematically shows a two-byte arrangement for an address mark AM. In this case, the number of continuous zero becomes rather long because a code with strong autocorrelation is used as the address mark AM. For this reason, when a prepit 1 is not completed in the area VFO2, the prepit becomes rather long as shown in (b) in FIG. 10, so that the amplitude of the tracking error signal becomes small, and the tracking control system becomes unstable. As a result, an erroneous count occurs in the number of jumped tracks during a seek operation, which is a problem. Accordingly, the prepit 1 should be completed within the area VFO2.
Third, when considering an area SM in the preformatting of the current ISO standards, for a 90 mm magneto-optical recording disk as shown in FIG. 11, and for a 130 mm magneto-optical recording disk as shown in FIG. 12, since a Long Mark Pattern is preformatted, the amplitude of a track error signal which is detected from the area SM is reduced, and the wave form is warped, so that not only does the tracking control system become unstable, but there is the problem that an erroneous count of the number of jumped tracks is produced during a seek operation. When taking this point into consideration, if the format configuration is such that the head of the sector is reliably detected even when the area SM is not used, the problem can be solved by omitting the area SM.